Whether a plastic labware item can go through a steam autoclave depends on two material properties, not on whether it “feels sturdy”: its heat deflection temperature (HDT) under load, and its resistance to hydrolysis (chemical breakdown) from repeated exposure to saturated steam. A standard autoclave cycle runs at 121°C (250°F) for gravity-displacement cycles, or up to 132-134°C for pre-vacuum cycles, both well above the melting or softening point of several common lab plastics. Guessing wrong warps, clouds, or embrittles the item — and in a load with other items, a melted piece can compromise the whole sterilization cycle.
Quick reference: which plastics survive the autoclave
| Plastic | Autoclavable? | Typical heat resistance | Notes |
|---|---|---|---|
| Polypropylene (PP) | Yes | ~135-171°C | The default choice for autoclavable labware (tubes, beakers, carboys); tolerates hundreds of cycles but can warp or discolor slightly over time |
| Polysulfone (PSU) | Yes | ~174°C HDT | Amber-tinted, rigid; used for reusable centrifuge bottles and connectors rated for thousands of cycles |
| Polyphenylsulfone (PPSU) | Yes | ~207°C HDT | Very high cycle-life, resists hydrolysis better than PSU; common in reusable medical/dental instrument trays |
| Polyethersulfone (PES) | Yes | ~203-216°C HDT | High clarity, used where PP’s slight cloudiness is unacceptable |
| Polyetherimide (PEI, e.g. Ultem) | Yes | ~200°C HDT | Amber, high strength; used for trays and instrument handles |
| PTFE (Teflon) / PFA | Yes | Continuous use to ~260°C | Chemically inert; used for stir bars, tubing, valve seats, o-rings |
| PEEK | Yes | ~152-160°C HDT (unfilled) | High mechanical strength; used for fittings and high-performance components |
| Silicone rubber | Yes | Stable well above 134°C | Tubing, stoppers, gaskets; retains flexibility across repeated cycles |
| Polystyrene (PS) | No | ~90-100°C HDT | Most disposable petri dishes and cell-culture plasticware; softens and deforms in the autoclave, which is why this labware is single-use/pre-sterilized, not reprocessed |
| Polyethylene (LDPE) | No | ~105-115°C melting | Squeeze bottles, bags; melts or badly distorts |
| Polyethylene (HDPE) | Limited | ~120-130°C melting | Some rigid HDPE containers survive occasional short 121°C cycles but deform with repeated cycling — check the manufacturer’s rating before relying on it |
| PVC | No | Degrades below autoclave temps | Can soften and release hydrogen chloride gas under moist heat; not autoclaved |
| Acrylic (PMMA) | No | ~85-100°C HDT | Clouds, warps, and can crack |
| Nylon (polyamide, PA) | Limited | Moderate | Some grades tolerate occasional autoclaving but absorb moisture and degrade with repeated cycles |
Why heat resistance alone doesn’t decide it
Two failure modes matter, not one:
- Thermal deformation: if a plastic’s heat deflection temperature is below the cycle’s set point, it softens, sags, or melts under its own weight or the load stacked on it. This is why polystyrene labware — fine at room temperature, common for disposable petri dishes and pipettes — is unusable in an autoclave even though a single brief exposure at a slightly lower temperature might not visibly ruin it.
- Hydrolytic degradation: saturated steam attacks the polymer chain itself in some plastics (notably polycarbonate and, to a lesser degree, some polyamides), even below their nominal heat-deflection temperature. The part doesn’t melt, but it becomes brittle, crazes, or yellows after repeated cycles — which is why some manufacturers rate polycarbonate labware for only a limited number of autoclave cycles even though its HDT (~130-140°C) technically clears a 121°C cycle.
This is also why autoclavable is a manufacturer-rated claim tied to a specific cycle type and count, not a fixed property of “the plastic” in the abstract — the same polymer resin can be formulated with different fillers, stabilizers, or wall thicknesses that change its real-world cycle life. Always check the item’s own autoclave rating (temperature, cycle count, cycle type) rather than inferring it purely from the resin name.
How to tell what a piece of labware is made from
- Resin identification code / plastic recycling symbol molded into the item (a number 1-7 inside a triangle) identifies the base resin family, though it doesn’t by itself confirm an autoclave rating.
- Manufacturer autoclave symbol: many lab-plasticware makers mold or print a small autoclave icon with a maximum temperature (e.g. “121°C” or “134°C”) directly on reusable items rated for reprocessing.
- Product datasheet: for anything going into repeated use, check the vendor’s stated maximum autoclave temperature and cycle count rather than assuming from the resin family alone — this matters most for borderline materials like HDPE and polycarbonate.
Practical guidance for lab use
- Default to PP, PSU, PPSU, PES, or PTFE for anything that will be autoclaved repeatedly (tips boxes, centrifuge bottles, tubing, stir bars) — these are the materials autoclave-rated reusable labware is built from for a reason.
- Never autoclave polystyrene, PVC, or acrylic labware — these are consumables meant to be discarded or pre-sterilized by the manufacturer (gamma irradiation or ethylene oxide), not reprocessed in-house.
- Treat HDPE and nylon as case-by-case — some rigid HDPE containers are rated for occasional short cycles, but check the datasheet before building a routine around it, and expect a shorter service life than PP or PSU equivalents.
- Load orientation matters even for autoclavable plastics: caps loosened (not sealed, to avoid pressure buildup and allow steam penetration), items not touching the chamber wall, and container material limits respected for whatever cycle (gravity vs. pre-vacuum vs. liquid) is actually selected — see the related autoclave-cycle guidance below for how cycle type affects load handling.
- Retire plastic labware once it shows visible degradation — clouding, crazing, brittleness, or warping after repeated cycles signals the material is past its rated cycle life, even for a nominally autoclavable resin.
Standards this ties into
Steam sterilization validation and routine control are covered by ISO 17665 (moist heat sterilization of health care products), and U.S. healthcare-facility steam sterilization practice follows ANSI/AAMI ST79. Neither standard specifies which lab plastics are autoclavable — that’s a materials-compatibility question the item’s manufacturer answers — but both govern how the cycle itself (temperature, exposure time, air removal) is validated and monitored, which is the other half of getting a sterilization load right. For how to confirm a given cycle actually reached and held sterilizing conditions, see CASRAI’s guide to autoclave validation using biological and chemical indicators.
Frequently asked questions
What plastic is autoclavable?
Polypropylene (PP) is the most common autoclavable lab plastic, followed by polysulfone (PSU), polyphenylsulfone (PPSU), polyethersulfone (PES), PTFE, PEEK, and silicone rubber. All of these have a heat deflection temperature comfortably above the 121-134°C range used in autoclave cycles and are formulated to resist repeated moist-heat exposure.
Which plastics are NOT autoclavable?
Polystyrene (PS), PVC, and acrylic (PMMA) should never be autoclaved — all three have heat deflection temperatures well below standard cycle temperatures and will deform, degrade, or in PVC’s case release corrosive off-gassing. Standard polyethylene (LDPE) also fails; rigid HDPE is borderline and needs a manufacturer check.
Is polycarbonate autoclavable?
Polycarbonate (PC) technically clears a 121°C cycle on heat deflection temperature alone (~130-140°C), and it is autoclaved in practice, but it degrades faster than PP or PSU under repeated moist-heat exposure — expect yellowing, crazing, and reduced clarity over dozens of cycles, and check the manufacturer’s rated cycle count rather than treating it as indefinitely reusable.
Can you autoclave a plastic labeled “microwave-safe”?
No — microwave-safe and autoclave-safe are unrelated ratings. Microwave safety is about dielectric heating and food-contact chemistry at typically well under 100°C; autoclave safety is about sustained pressurized steam at 121-134°C. Always check for an explicit autoclave rating, not a microwave-safe label.
How many times can you autoclave the same plastic item?
It depends on the resin and the manufacturer’s rating — PP and PSU items are commonly rated for hundreds of cycles, while borderline materials like HDPE or polycarbonate may be rated for a much smaller number before mechanical or optical degradation. Inspect for clouding, brittleness, or warping and retire the item once it appears, regardless of the nominal rating.
For related equipment guidance, see CASRAI’s guides on autoclave cycle types, autoclave operating safety, autoclave troubleshooting, and autoclave validation with biological and chemical indicators. For general material compatibility beyond heat alone, see the chemical compatibility chart for wetted materials.
